How do I add the content of an environment variable to a file in windows batch?

Question

Under windows, I would like to add the content of an environment variable, say JOB_NUMBER to a file, say C:\\job_numbers.txt .

Example: The file is empty and JOB_NUMBER contains the value 100. I want the content of the file C:\\job_numbers.txt then to be

100

When I repeat this step and JOB_NUMBER now contains the value 101, I want the content of the file C:\\job_numbers.txt then to be

100
101

(so each new addition in a new line).

How can I achieve this in windows batch without a complicated mechanism and without installing something else?

Answer 1

>>"C:\job_numbers.txt" echo %job_number%

Note that the quotes are only required if the filename contains spaces; they're harmless otherwise.